SynopsisThe mutual miscibility of random poly( styrene-co-methylmethacry1ate)s with different compositions hut a constant molecular weight of M , 150,000 was studied at room temperature and at 180°C. Compatibility was analyzed with films cast from solutions with different solvents. The reliability of the analytical technique is discussed. The miscibility windows { x , y , } , which define the limits of miscibility of the blends of a given copolymer P(S,MMAI-,) with other copolymers P (S,MMA,,), were determined for all x. The widths I xy z I of these windows are, contrary to the predictions of the Flory-Huggins model, different for yx > x and yx < z, and depend strongly on x . Miscibility is better for blends with a high MMA content. The windows are markedly wider at room temperature. Many blends are, therefore, "semicompatible," i.e., have a critical point of the LCST type between room temperature and 180°C.

The miscibility of copolymers AxB1−x and AyB1−y, derived from the same monomer pair (A, B) but differing in composition, was studied. The systems (A, B) were (S, MMA), (BMA, MMA), (S, BMA), and (CIS, BMA) (S: styrene, CIS: p‐chlorostyrene, MMA: methylmethacrylate, BMA: n‐butylmethacrylate). Miscibility diagrams were recorded, at low and high temperatures, using cast films and dry films. All blend systems feature hightemperature miscibility gaps. Unusual effects of the compositions x and y on miscibility in blends AxB1−x/AyB1−y were observed. The classical prediction that miscibility should depend only on the composition difference |x – y| usually is too simple. It appears necessary to consider dyad interactions.

The glass transition temperatures Tg of homogeneous binary blends of the homo-and the statistical copolymers of the system poly(styrene-co-methyl methacrylate) were studied. Some of the blends, which are in the equilibrium phase separated, were forced into homogeneity. Tg (9) of the homopolymer blends (PWPMMA)? follows the Fox equation, while Tg (x) of the pure copolymers P(SXMMA1-,) exhibits a minimum. This minimum can be effectively removed by blending the copolymers with small fractions (@ x: 0,2) of one of the two homopolymers or a differently composed copolymer P(S,MMA, -,).

SUMMARY:The anionic solution polymerization of glycolid yielding polyglycolic acid was examined with several solvent-initiator-systems. The polymerization behaviour in toluene using the tertiary amines triethylamine and N,N-dimethylbemylamine as initiators and in sulfolan (tetrahydrothiophenedoxide) with N,N-dimethylbenzylamine is described in dependence on initiator concentration and reaction time.

Miscibility can particularly easily be “tailored” with blends P (AxB1‐x)/P (AyB1‐y) of random copolymers and with blends P (Ax‐b‐B1‐x)/P (Ay‐b‐B1‐y) of diblock copolymers, where the blend components differ only in composition. The former class of blends is discussed in some generality, the latter only in one special example, where the components are a homopolymer (x=0) and a symmetric copolymer (y=0.5). Phase diagrams and phase morphologies are shown.